docs: def _populate_sub_entity(self, entity, type_name):
          """
          Simple API-backed cache for populating MyGeotab entities
  
          :param entity: The entity to populate a sub-entity for
          :param type_name: The type of the sub-entity to populate
          """
          key = type_name.lower()
          if isinstance(entity[key], str):
              # If the expected sub-entity is a string, it's a unknown ID
              entity[key] = dict(id=entity[key])
              return
          cache = self._cache[key]
          subentity = cache.get(entity[key]['id'])
          if not subentity:
              subentities = self.api.get(type_name, id=entity[key]['id'], results_limit=1)
              if len(subentities) > 0:
                  subentity = subentities[0]
                  entity[key] = subentity
          else:
              entity[key] = subentity